Rescue workers who are searching the wrecked Italian cruise ship Costa Concordia say the time has come to accept that there is no chance of finding more survivors.

Rescue workers have so far found 16 bodies of people who died after the cruise liner hit rocks off the coast of Tuscany on January 13.

Teams of searchers on three ships are also scouring the seabed for the bodies of people who may have been trapped under the cruise liner as it toppled over.

"We have gradually to accept the idea that in those conditions there is no more hope of survival," said Italy's civil protection agency head, Franco Gabrielli, who is running operations at the site of the Costa Concordia.

Thirteen bodies have been identified so far and 16 people are still officially missing.

ARPAT, the Tuscan agency for environmental protection, said that there was no longer concern over a leak of surfactants - substances present in detergents - from the wreck, as workers prepared to siphon off the ship's oil.

Tests on Wednesday had shown levels close to those found in industrial ports.

"It seems to have been a limited phenomenon. By now there is no longer a problem and the six control tests carried out are all negative," said Marcello Massa Ferri, an ARPAT representative who spoke at a daily press conference.

The liner, beached on rocks off the idyllic island, contains 2,400 tons of fuel as well as toxic liquids, cleaning products and chlorine for four swimming pools, all of which could leak and cause an environmental disaster.

Free trade is the oldest argument in federal politics and the issue that literally defined the federation era but opposition exists to the TPP, courtesy of the Investor-State Dispute Resolutions clause.